Preheat your oven to 425°F (220°C). This gets the potatoes nice and crisp and the chicken skin beautifully browned.
Rinse and pat dry the chicken thighs. In a large bowl, toss the chicken with half of the olive oil, rosemary, thyme, garlic, salt, and pepper. Let it sit while you prep the potatoes.
Wash the potatoes and cut them into even pieces so they cook at about the same rate as the chicken. Toss them with the remaining olive oil, a pinch of salt, and a crack of pepper.
Spread the potatoes on a large rimmed baking sheet or in a shallow roasting pan. Place the chicken thighs on top of the potatoes, skin-side up. If you have extra rosemary, sprinkle a bit more on top.
Roast in the oven for 25–30 minutes, then check for doneness. The potatoes should be tender and golden, and the chicken should reach an internal temperature of 165°F (74°C). If needed, give it a few more minutes to crisp up. If the chicken skin isn’t as crisp as you’d like, switch to broil for 1–2 minutes watching closely.
If you’re using lemon juice, drizzle it over the tray right after you pull it from the oven. A quick squeeze of fresh lemon over the finished dish brightens the flavors.
Optional finish: melt a tablespoon of butter and drizzle it over everything just before serving for extra gloss and richness. Garnish with chopped parsley if you like.